تعدد الأشكال الجيني لـ BRCA1 وBARD1، ومثيلة محفز BRCA1، ومستويات البروتينات ذات العلاقة لدى النساء المصابات بسرطان الثدي في مدينة كربلاء

BRCA1 and BARD1 Gene Polymorphisms, BRCA1 Promoter Methylation, and Related Protein Levels in Women with Breast Cancer of Karbala City

Abstract

The current thesis presents the first comprehensive molecular characterization of breast cancer in women from Karbala governorate, Iraq, addressing a critical knowledge gap in a population with high disease incidence (80 per 100,000). Breast cancer remains the most prevalent female malignancy globally, affecting 1.4-2.3 million women annually, with Iraq reporting 8,708 cases in 2023 alone. While international research has established the significance of BRCA1/BARD1 genetic variants, epigenetic modifications, and molecular biomarkers in breast cancer, no systematic investigation had been conducted in the Iraqi population. Thus, this study aimed to evaluate the associations between genetic polymorphisms (BRCA1 rs4986850 and BARD1 rs1048108), BRCA1 promoter methylation, protein expression levels, and miR-498 expression with breast cancer risk and clinical outcomes in this understudied population. A case-control study was conducted, to attain this goal, recruiting 188 women (90 breast cancer patients and 98 healthy controls) from Karbala between November 2024 to June 2025. The analysis included genetic polymorphisms (BRCA1 rs4986850 and BARD1 rs1048108), BRCA1 promoter methylation, protein levels (BRCA1 and BARD1), and microRNA-498 expression using PCR, sequencing, ELISA, and real-time PCR techniques.
The demographic analysis revealed significant risk factors unique to this population, including low education levels (47.8% of patients had only elementary education), extensive hormone replacement therapy use (65.6% vs 8.2% in controls), and younger age at first childbirth (20.5 vs 26.0 years). Clinically, patients presented with advanced disease, as 81.1% of tumors exceeded 20mm and 65.6% showed lymph node involvement, despite 86.7% being hormone receptor-positive. The genetic analysis yielded a novel protective finding: the BARD1 rs1048108 AA genotype conferred 66% reduced breast cancer risk (OR=0.34, p=0.014), with the A allele providing 37% protection. BRCA1 promoter methylation was significantly elevated in patients (17.8% vs 13.3%, p=0.043), accompanied by dramatic reductions in both BRCA1 (4.194 vs 7.887 ng/ml) and BARD1 (3.991 vs 10.053 ng/ml) protein levels. Notably, BARD1 protein demonstrated exceptional diagnostic accuracy with 93.6% area under the curve, 88.5% sensitivity, and 95.8% specificity.
The molecular correlation analysis revealed critical disruptions in cancer patients. The normal positive correlation between BRCA1 and BARD1 proteins (ρ=0.464) was lost in cancer patients, indicating compromised DNA repair mechanisms. Conversely, a novel correlation emerged between miR-498 (which was upregulated 3-fold in patients) and BRCA1 protein exclusively in cancer cases (ρ=0.475), suggesting aberrant regulatory networks. Biochemical analyses confirmed systemic effects, including elevated inflammatory markers (hs-CRP: 8.18 vs 2.00 mg/L) and reversed albumin/globulin ratios. These findings establish population-specific molecular signatures that differ from global patterns, highlighting the importance of localized research for effective cancer management.
Based on these discoveries, several evidence-based recommendations emerge for improving breast cancer outcomes in Karbala. Implementation of screening programs incorporating BARD1 protein testing should target women over 40, particularly those with limited education or hormone therapy exposure. The exceptional diagnostic performance of BARD1 protein, measurable through simple blood tests, makes it particularly suitable for resource-limited settings. Genetic counseling services must address the protective BARD1 variant while public health campaigns should urgently address the exceptionally high hormone replacement therapy use. Treatment protocols require adaptation for the predominantly hormone-positive, locally advanced presentations characteristic of this population. This pioneering study transforms understanding of breast cancer in Iraqi women, providing crucial molecular data that can guide targeted interventions, improve early detection, and ultimately reduce the substantial disease burden in this high-incidence region.